Open-flame heated continuous furnace



Sept. 28, 1948.

F. N. HAYs 12,450,081

OPEN-FLAME HEATED COTINUOUS FURNACE Filed April 27, 1944 5 sheet-sneet 1Fei@ /V. Afm/5.'

Sept. 28, 1948. F. N. H'AYS OPEN-FLAME HEATED CONTINUOUS FuRNAcE.

3 Sheets-Sheet 3 Filed April 27, 1944 Petented Sept. 28, i948 UNITEDSTATI-:s PATENT OFFICE vFred N. HaynEdgewood, Pa.

Application April 27, 1944, Serial No. 532,996

This is a continuation-impart of an application filed May 20, 1942,Serial No. 443,801, and relates to open-flame heated continuous furnacesand particularly to the type having fiues ar ranged to provide.,sectionalized heating of the 5 work traveling through the furnace, theobject being to provide a furnace of this type which may be operatedwith the atmospheric pressure level inside the furnace in its hightemperature zone adjusted about at the hearth or work top level andwhich does not require that the pressure vat the hearth level in thehigh temperature zone be materially above atmospheric pressure to makethe flue system work, the latter practice being objectionable since itblows the hotter flame 2 Claims. (Cl. 263-43) stingers through thevarious furnace openings to Figure 3 is a view similar t'o Figure 1except for showing a modication of the invention.

More specifically, in the case of the first example the furnace is ofthe continuous type having a work entrance I for one end and a workexit2 for its other end with a hearth 3 over which the work travelswhile going from the entrance to the exit. The furnace is heatedbyhaving at least one open-name burner 4 near the exit 2 and provision ismade for sectionalized heating of the work by the furnace having atleast one flue 5 near the exit 2 and at least one other flue 6 near theentrance I in conjunction with having a roof providing a. lower portion1 near the entrance l and a higher portion 8 near the exit 2.

The work travels through the furnace on skids i and, preferably, thefurnace is provided with at least one other burner I0 beneath the skids8 that are under the lower roof portion 1. In a furnace of any materialwidth there is a row of the burners 4 and a rowof the burnersl l0extending transversely of the furnace, and the flues 5 and 6 are usuallyeach in the form of a multiplicity of flue passages extending in a rowtransversely of the furnace, al1 to the end of obtaining laterallyuniform heating. The flue 5 is provided with a damper I l and the flue 8is provided with a damper l2, both fiues connecting with a stack I3 byway of a stack connection flue il common to both the flues 5 and 6 butwhich functions to provide a longer stack connection for the flue and ashorter stack connection for maintenance of the atmospheric pressurelevel 2 the flue 6 as these` connections compare to each other inlength. This means there is more aucl. tion available in the ue 6 thanin the ilue 5.

In operation, the work is introduced to the `skids 9 through theentrance I and is then moved over the skids through the furnace until itis at the exit 2 from which it is withdrawn. At least the burner 4' isoperated and due to the height of the roof portion 8 there is created ahigh temperature zone beneath this roof portion, at least some of theproducts then exhausting through the flue and forming a low temperatureor preheating zione beneath the lower roof portion 1, the dampers I Iand I2 being operated as required to maintain the high temperature zonebeneath the higher roof portion 8 at the temperatures demanded to bringthe work to proper temperature. The burner I0 is operated as required toheat the bottom of the work to attain a relatively uniform preheating ofthe work prior to its reaching the high temperature zone.

The present invention is characterized by positioning the lflue 5, whichis the one near the exit 2, at least adjacent the level of the hearth 3and not therebelow, although this flue may be slightly above the levelof the hearth. Since it is preferable to maintain the atmosphericpressure level, in the high temperature zone, at about the hearth level,or very slightly thereabove so that it comes about at the level of thetop of the work being heated, the flue 5 should not be placed so high,such as in the roof portion or above the burner 4, as to result in aconstruction preventing the at or close to the level of the hearth. Withthis arrangement of the flue 5 it exhausts the furnace atmosphere at apoint where this atmospherehas a pressure that about at least equals theatmospheric pressure, or which is slightly above atmospheric pressure.so the flue 5 can function properly in spite of its long stackconnection, which reduces the suction available by reason of the stackeffect, and without raising the pressure of the furnace atmosphere inthe high temperature heating zone beneath the higher roof portion 8 to adegree resulting in the excessive blowing of hot flame stingers throughthe various furnace i hearth l, while the latter terminates short ofthis wall, the exit. being in the form of an exit Il through this wall,having the flue il. and at a position beneath the flue I5, that is nearthis exit II, the furnace having means for carrying work from the hearthl down through this exit Il, which means is in the form of a skiddecline l1. With this arrangement the atmospheric pressure level mayalso be maintained close to the hearth level l, or at this level, in thehigh temperature zone and still have the ue Il function properly, eventhough it is provided with the longer stack connection, the ue Il againbeing adjacent the level of the hearth 3 but not therebelow. In thistype of furnace-it was formerly thought necessary to .position the flueI5 beneath the decline I1 so as to prevent air .sucked in through theexit` I8 from going to the high temperature zone beneath the roofportion 8, but it i s to be noted in the construction disclosed hereinthat air cannot go into this high temperature zone because the positionvof the flue I5 permits the positioning of the atmospheric pressurelevel existing in this zone about at the hearth level, the pressureabove this level being above atmospheric pressure and thereforeexcluding the possibility of air being sucked into it. Furthermore, anyair that might get sucked in merely short circuits from the exit to theiiue I5 without cooling the high temperature zone. As explained in thecase of the first example, the ilue I5 is provided by a multiplicity ofrlues extending transversely of the furnace in the case of a furnace ofany material width.

Both examples are intended to heat metal bars moved transverselykthrough the furnace in contact with each other on the skids 9, the barsbeing introduced and removed longitudinally through the exits I and 2 inthe case of the iirst example, while the second example is of the typehaving an entrance I8 through which the bars may be introducedlaterally, the exit i6 likewise beingwide enough so that the bars candischarge laterally, which means that the bars are not 1ongitudinallyintroduced and removed in the case of this second example. Since thebars contact one another the atmospheric pressure level may be lifted byproper operation of the furnace to about at the level of the tops of thebars, their i contact with one another and the fact that their bottomsare shielded by the hearth 3 reducing the hazard of oxidation. If thebars were separated, or were other objects which could not providemutual protection by intercontact, it would be better practice to lowerthe atmospheric pressure level. again by proper operation of thefurnace, to about the level of the hearth. In either case the iiues land Il function properiylwithout greatly increasingv the furnacepressure for the purpose of making the nues operate.

I claim:

1. In a continuous heating furnace having a horizontal hearth adapted tosupport work in its travel through the furnace, a roof and wallsenclosing said hearth, a work entrance and a work exit in the wallsadjacent opposite ends of said hearth, at least one open flame burneradjacent the work exit, atleast one nue opening adjacent the workentrance, at least one iiue opening ad jacent the work exit, and stackconnections for said nue openings, the improvement which compriseshaving the lower limiting position of said iiue opening adjacent thework exit at the level of the horizontal hearth, which enables thefurnace to be controlled with the atmospheric pressure level at hearthlevel. i

2. In a continuous heating furnace having a horizontal hearth adapted tosupport work in its travel through the furnace, a roof and wallsenclosing said hearth, a work entrance and a work exit in opposite endwalls, at least one open name burner adjacent the work exit, at leastone ue opening adjacent the work entrance, at least one iiue openingadjacent the work exit, and stack connections for said ue openings, theimprovement which comprises locating said ilue opening adjacent the workexit in the end wall above the level of the horizontal hearth to enablethe furnace to be controlled with the atmospheric pressure level athearth level.

FRED N. HAYS.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES rlrirnrs` Number Name Date 1,729,411 Akin Sept. 24, 19291,912,933 Culbertson... June 6, 1933 2,157,221 Spencer May 9, 19392,180,089 McDermott Nov. 14, 1939 2,329,211 Morton Sept. 14, 1943 OTHERREFERENCES Sketch V1'. Fig. 141, p. 190, of Trinks "Industrial Furnaces,vol I, 3rd edition, 1934. (A copy of this reference is in Div. 28.)

